@article{DE_1978_14_5_a23,
     author = {A. E. Rudenok},
     title = {Isolated periodic solutions of certain differential equations},
     journal = {Differencialʹnye uravneni\^a},
     pages = {935--937},
     publisher = {mathdoc},
     volume = {14},
     number = {5},
     year = {1978},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1978_14_5_a23/}
}